Art with power spectrum estimation
Above is a estimation of power spectrum for a large number of very closely spaced concentric circles (see equation below). A two dimensional Welch method was used to estimate the spectrum. Aliasing is the source of this neat effect. Note that fftshift has not been performed so that zero frequency is represented on the four corners of this plot. I used the same power spectra estimation algorithm I use for my research.
Above you see the actual signal plotted. Notice that it doesn't look very much like concentric circles at all (although the equation below states that it should). This is because the distance between pixels is smaller than the distance between the circles so makes kind of its own aliasing-like effect.
signal=sin(((20x)^2+(20y)^2)^4/10)Below is another example with slightly different parameters and inverted colors but it is the same concept.